FEBRUARY 28, 2007

Tampa, Florida

This document is available in
alternate formats upon request to Dept. of Community Affairs, Codes &
Standards, 2555 Shumard Oak Blvd.,
Tallahassee, FL32399, (850) 487-1824.

ENERGY
EFFICIENCY AND MOISTURE CONTROL IN THE FLORIDA
CLIMATE

REPORT TO THE FLORIDA
BUILDING COMMISSION

FEBRUARY 28, 2007

Issue Overview

As a result of an identified need, Chairman Rodriguez
announced to the Commission and members of the public that there will be a “Symposium
on Energy Efficiency and Humidity Control in Florida Homes”. The idea for the
Symposium derived from discussions at the Energy Code Work Group meetings,
primarily between the window manufacturers and air conditioner manufacturers.
The Workgroup process identified the need for a technical forum to discuss how
energy efficiency measures that effect "sensible heat" gains impact
air conditioning equipment's ability to control indoor humidity. Industry
stakeholder put this workshop together with the help of Commission staff. The
goal of the Symposium is to create a broader base of understanding on how
building envelope energy efficiency measures interact with air conditioning
systems so we can better plot a strategy to improve energy efficiency
while maintaining healthy indoor environments.

The “Symposium on Energy Efficiency and Humidity
Control in Florida Homes” was held on February 28, 2007 in Tampa,
at the Doubletree Hotel, TampaWestshoreAirport
location.

A major portion of the energy used to cool homes in Florida’s humid climate
is due to moisture condensing out of the conditioned indoor air. This portion
of the energy is referred to as the “latent load” because to get water vapor to
condense to liquid water the “latent heat of fusion” must be removed by the
air-conditioner. (For the science minded folk, latent heat of fusion is the
amount of energy that has to be removed to convert water vapor to a unit of
liquid water with no change in temperature.) When the air-conditioner does not
remove enough water vapor from the indoor air the humidity in the home reaches
equilibrium at a higher level. Where indoor air humidity is too high moisture is
absorbed in furnishings and combines with organic matter like dust and dander
to provide a good environment for mold, mildew and dust mites. Also, when
indoor air is at elevated moisture levels, the ability of the air-conditioning
system to dry-out the rainwater that leaks into walls and remove outdoor air
water vapor that permeates the walls is reduced. (Explanation: The water vapor
pressure difference between indoors and outdoors results in moisture trapped in
walls diffusing more toward the indoors in the hot and humid climate. The
higher the indoor humidity level compared to outdoors, the less drying occurs.)
This moisture in walls can also lead to mold and mildew growth on paper wrapped
gypsum board and wood members and provide an environment favorable to termites
as well as mold.

Energy used to cool homes is due to two factors. The “latent
heat load” due to condensation of water vapor and “sensible heat load” which
relates to changing the air temperature. Sensible heat from solar radiation and
hotter outdoor air temperature is transmitted through the ceilings, windows,
walls and floors and heats up the indoor air. Sensible load removal by the
air-conditioner results in cooling down the air. In dry climates like the US
Southwest and most of the West and Central US,
latent loads are insignificant. In other temperate zone climates latent loads
are more significant and equipment design must provide a latent removal
capacity, but latent becomes most important in the hot and humid climates of Florida and coastal-influenced regions of other Gulf states. A
comparison developed for reference indicated the latent portion of the energy
used for cooling in Pheonix, Arizona
over a season is 0% and the latent portion of the energy used for cooling the
same house over a season in Florida
is 20%.

When establishing building energy conservation regulations
for hot and humid climates special attention must be given to latent energy
loads, both because they are a major component of energy use and because
increasing efficiency by only controlling sensible heat loads can result in an
imbalance that enhances mold and mildew and degrades indoor air quality.

The challenge the Commission faces in setting energy
conservation regulations for buildings is how to maintain a balance of
requirements that address sensible and latent loads and result in healthy
indoor environments. The evolution of the Florida Energy Code has addressed
this balance successfully by taking significant steps to control latent load
when major steps were taken were taken to reduce sensible load.The first major change in criteria addressing
sensible load increased wall and ceiling insulation requirements to R-19 and
R-30, respectively, and reduced allowable sensible load due to solar heat gain
through windows. The Code established concurrent latent load control through
requirements for sealing the building envelope to limit humid outdoor and attic
air from infiltrating indoors. The next major step in building efficiency came
when federal law imposed higher minimum efficiency requirements on
air-conditioners. The equipment designed to meet those standards sacrificed
latent load capacity so the Florida Energy Code enhanced air distribution
system sealing requirements and air-conditioning system sizing requirements. It
followed with requirements to ensure balanced air pressure in homes to which
limit the depressurization of spaces that drives humid outdoor air indoors. As
the state refocuses on energy independence and potential contributions of
conservation of energy use for building cooling, attention must be paid to
addressing humidity control in parallel with the national efforts to improve
energy efficiency through reduction of sensible loads.

The most recent change in standards to effect sensible heat
loads is the federal regulations that increased minimum efficiency for
air-conditioners from SEER 10.0 to 13.0. As with the first change to minimum
efficiencies for the air-conditioners, there is concern that the new equipment
may have marginal capability of maintaining healthy indoor humidity control.
This is in part due to the new equipment itself but is also due to sloppy
design and construction practice in the air-conditioning service industry. Two
primary factors can combine with the reduced moisture removal capability of new
equipment to increase the number of humidity control problems: the sizing and
selection of air-conditioning equipment and air distribution (duct) systems.
Both have been addressed by requirements in the Energy and Mechanical Codes but
widespread failure to comply with and enforce those requirements often result
in the potential for a significant increase in system failures and unhealthy
homes.

Two factors led to the organization of the
Commission-sponsored symposium on energy efficiency and humidity control of
February 2007. First, the uncertainties regarding humidity control with current
construction practices and new air-conditioning equipment complying with
federal SEER standards. Second, the renewed interest in energy conservation by
the Florida Legislature and advocacy for national efficiency standards at the
Commission. The purpose of the symposium was to educate non-air-conditioning
professionals on the humidity control challenge and to identify actions that
can be taken and options that can be pursued to maintain humidity control and
healthy environments while enhancing energy conservation standards for Florida buildings.

Symposium participants identified two major options to be
pursued through several actions. The first, and potentially most difficult, is
education of the air-conditioning service industry, homebuilders and consumers
about the humidity control and indoor air quality problems resulting from
equipment over-sizing and poor air distribution systems. The second is to work
with equipment manufacturer’s research and development teams to develop design
parameters for equipment that can reliably increase the latent load removal
capacity of equipment. The three major manufacturers represented at the
symposium committed to working on improved equipment. These two paths provide
the Commission with opportunities to keep in balance, while advancing, the two
primary policies of the State:, energy conservation and healthy indoor
environments.

Simplified Description of Humidity Control by Air
Conditioning Systems:

Air- conditioners control indoor humidity by moving air
across the indoor cooling coil where water vapor condenses on the coil’s fins.
The water vapor condenses only while the fins in the cooling coil are at a
temperature below the “dew-point temperature”. The colder the fins the greater
the condensation rate and the more moisture is removed from the air.

Two factors in air-conditioner equipment performance have
changed to achieve the SEER 13.0 efficiency ratings required by the federal
government. Average operating temperatures over a run cycle have gone up
(reducing moisture removal capacity) and fans run longer after the compressor
shuts down in order to take advantage of all of the compressed refrigerant and
the energy it took to compress it. Running fans after the compressor cuts off
not only allows the cooling coil to go above the dew-point temperature
(preventing so water vapor/moisture from being condensed out of the air) but
also causes condensed water on the coil to be re-evaporated and pushed back
into the living space.

How much water vapor is removed from the house during a run
cycle depends on how long the system runs at a condition where the cooling coil
is colder than the dew-point temperature of the indoor air. The greater the
start-up and run-down portion of the total run cycle, the lower the water
vapor/moisture removal capacity of a system. Multiple short cycles will have
greater total start-up and run-down portions of the total run time than long
runtime cycles. So short-cycling of air-conditioners results in less moisture
being removed from the conditioned air.

Short cycling occurs when the
equipment is oversized. The system is turned off and on based only on the
indoor air temperature, which is driven by “sensible” heat gains. Conventional
air-conditioning systems are not “load matching” though there are complex
multiple compressor systems available
that are staged to better match the different rates of heat gain into a home
that occur at different times of day. Conventional systems are off-on,
delivering all of their cooling capacity or none. Equipment capacity depends on
outdoor and indoor conditions (the hotter it is outdoors the less the
capacity), but it does not track the rate of heat gain into a home--so it is
not “load matching”. In operation, the thermostat (which senses are temperature
and not moisture content), allows the temperature in the house to rise a set
number of degrees above the temperature control setting before turning on the
system. This allows a sensible load to build up in the house like a charge in a
battery. How quickly the heat load is removed by the air-conditioner depends on
its capacity (it’s size, usually referred to as “tons”). Four ton systems cool
the air in a shorter time than three ton systems and, therefore, have a shorter
run cycle.

The objective of air-conditioning
equipment sizing and selection is to match the equipment capacity to the worst
condition likely to occur on regular basis. Typically, systems are designed for
a condition that will be the worst to occur 97.5% of the time. This provides
smaller capacities that match the normal daily loads as they change through the
day and night in response to outdoor temperature and sunshine. Smaller
capacities result in longer run times to remove the sensible loads. Longer run
times mean more water vapor removal and lower indoor humidity. Oversizing
results in shorter run times, less water vapor condensed out of the air, and
higher indoor humidity.

When air-conditioning contractors
oversize (typically because they want to avoid call backs), or home builders
and home owners demand large capacity equipment (they think larger is better),
short cycling will result and humidity control will be problematic.

A separate contributing factor to
over design of systems is “hot spots” in homes. Hot spots and damp, musky spots
result from improperly designed and installed duct systems, which do not
deliver adequate conditioned air to those spots. The simple-minded solution is
to increase the system size to provide more cooling. This in turn causes
systems to be larger than the total design loads for the home and creates short
cycling. Poor duct systems also cause indoor humidity control problems by not
providing enough air movement or mixing. The delivery air is at a lower
humidity and reduces the humidity in the home by mixing with higher humidity
air. When the air quantities and velocities are reduced by constrictions in the
duct system, spot humidity (typically in remote or closed rooms and closets)
can rise, leaving a damp feeling and musky odors.

Oversized equipment and poor air
distribution duct systems are ubiquitous in the industry today. These system
design and installation errors, combined with reduced latent energy removal
capacity of the new higher efficiency air-conditioners, create an increased
risk of failure to obtain adequate control of indoor humidity. This, when
combined with other water control failures in building structures, can result
in mold, mildew and other biological contamination and degraded indoor air
quality.

FORUM OVERVIEW

Opening

The Energy Forum was convened
at approximately at 8:00 AM.

DCA
Staff Present

Rick Dixon, Mo Madani, and Ann Stanton.

Meeting Facilitation

The question and answer session, issues discussion, and next
steps were facilitated by Jeff Blair from the Florida Conflict Resolution
Consortium at FloridaStateUniversity.
Information at: http://consensus.fsu.edu/

Forum Objectives

The following objectives were outlined for the Forum:

üTo Identify the Relationship of Sensible Heat
Load and Air Conditioning System Performance to Moisture Control In Florida
Homes

üTo Discuss the Effect of Heat Gain Through
Windows on Sensible Heat Loads

üTo Identify the Sensible and Latent Heat Removal
Performance Characteristics of Current Air Conditioning Equipment and Control
Strategies

üTo Identify the Capabilities of the Air
Conditioning Service Industry to Implement Equipment Measures for Effective
Moisture Control

üTo Assess the Potential Risk for Loss of
Moisture Control When Major Reductions of Sensible Gains are Paired with
Current Equipment

üTo Identify Steps that Can be Taken to Reduce
the Potential Risk if It Is Significant

Presentations

The following presentations were made to Forum participants
in order to frame the issues and provide technical information for developing
recommendations to address the issues. The presentations were given on
PowerPoint and are included as attachments in PDF format.

Panelist Question
and Answer and Discussion Session

At the conclusion of the presentations the six presenters
served as a panel to answer questions, define the problem, identify issues that
must be addressed, prioritize the issues/options, and to decide on next steps.

A driver on humidity with modern type construction is how
the occupants live.Our mission is to
seal the envelope, especially attic.How
can they properly account for the tightness of a building?Re:sizing of cooling & ventilation equipment.

Answers: (Bob) I understand that new parameters (in sizing
calc) include tight, semi-tight, loose construction.Generally run with semi-tight.I’m encouraging builders to put in quieter
bath fans, close to shower.The ACCA J
value of 1200 – 1800 Btu is close to correct.

Get calls from homeowners who don’t have window treatment
yet & the homes are hot.Know the
sizing is close.

(Chris)Air leakage load is challenge.Need to measure it.Have techniques to measure.Justify values used in load calc.Get more involved in duct testing, blower
door testing, air sealing, etc.When you
get up into better glass, the issue of window treatments goes away.

(Bob)No.Get hold of CILB.Need mandated 2
hours training for every contractor. Think low E glass is excellent.Do we have units that can handle it? Yes, but
costly. Would like a two year window to get HVAC contractors on board.

(Chris)Education is essential.Disagree with Bob on timeline.Technology is not new in US, just Florida.HVAC & window guys need to be best
friends.Need to make the clarification
that we should call it low SHGC windows.

Philip Fairey, FSEC.I see a small misconception.If we were to mandate a 0.4 SHGC, it would do
nothing to change energy use overall because it is in the baseline.

Roger Sanders, Energy TAC.Have had discussions on this subject. Feel
that no progress on energy conservation unless have good enforcement.Until we have directives from the contractors
that they want to do it right, won’t accomplish anything.Need incentive.People need to care.It all boils down to dollars & cents.

(Chris) You’re absolutely right;
if not inspected right won’t get results.

Tina Neace.HVAC Design.Have impact of improperly done Manual Js.Bob, were you talking HVAC contractors, or
include building contractors.Can’t get
actual facts about what’s going into the building.Building departments aren’t even looking for
Manual J.

(Rob) Dennis had asked if the A/C
had been downsized based on sizing calc. No, 4 ton units were put in both test
houses.

Gary Griffin, B&I Contractors,
FBC.In terms of understanding issue of
low E glass, if settle on 0.4 SHGC glass, value of glass on different
orientations needs to be brought into the equation.Second issue:Want to see higher efficiency products and change without causing
problems.It should be at a pace that
will not create sick buildings.Do we
need the code to define whether we have a problem?

(Chris) There is 0 correlation
between sick buildings and low SHGC glass.In 1997, IECC & ASHRAE adopted 0.4 SHGC.RE orientation:Trouble is that without low SHGC glass, not
just a west-facing issue.

(Rob) Benefit when spending
limited dollars does differ.Cost
benefit is small in some cases.Performance code puts in % glass.With tightening of the code and lower cost of windows, seeing more
efficient windows going in.

Rick Dixon, FL DCA.When planning for more energy efficient
buildings, we have taken steps to keep [avoid?] major shock in code.Need to solve issue with HVAC industry to
insure more energy efficient buildings in future.Real problem is that majority of industry is
not there.Mother’s home new a/c.Very bad practices seen.

Arlene Stewart:Have heard hard to get information from
builders. Have heard that windows drive the load.Know that 0.4 SHGC not currently being used.If we did have a cap of some sort, would it
make education, stocking, planning easier.Takes guesswork out of picture. No longer becomes high cost.

(Bob) Point is well taken. Would
like to see timeline to get contractors to where they need to be.

(Jeff)Agree that education is the key to the whole
thing.Company is selective on who they
sell equipment to.Not all competitors
take this position.Speaking to Manual
J:can get any answer I want.Design criteria has to be done right.

Arlene Stewart:Need to simplify things.Education is not an easy thing to do.Manual J may be the more important
calculation to focus on.

Pete Quintela:Building a better building is all about.Code does not state who enforces the energy
code. Often done by Mechanical plans examiner & inspector—who are not
certified to inspect feature that they are not trained to inspect.Much more involved.This is beyond the scope of his license.Need to catch the mouse, need better
mousetrap.

Jim Larson, Cardinal Glass Industries.Discussion of windows being the culprit.Not just windows. Nothing to limit load
calculation oversizing…need to prove the load. Simple limit that must be
disproved.

(Rob)National scope trying to take gamesmanship
out of the equation.

(Philip Fairey)You can get any number out of Manual J that
you want.Doesn’t mean done
correctly.National HERS specify how
Man. J is used:interior temperature
conditions, % design conditions, bathroom vent fans.Need standard for how it is done.

Identification of Key Issues and Prioritization Exercise

The facilitator, Jeff Blair, asked the panelists to identify
what they believed to be the key issues that should be addressed in order to
consider energy efficiency and moisture control in the Florida environment. Jeff proposed some
issues based on public comment and panelist discussions, and the panelists
agreed on 8 key areas. The issues were then prioritized, and finally additional
comments and discussion was solicited. Following are the results of the prioritization
exercise:

RANKING SCALE

5Highest Level of
Priority; Urgent

4High Priority

3Moderate Level of
Priority

2Low Level of Priority

1Lowest Possible
Priority; Group Should not Pursue

ISSUE

RANK

5

4

3

2

1

RAW SCORE

Proper design considerations/ standards (sizing)

1

6

0

0

0

0

30

Education & training on how all components interact.

2

2

4

0

0

0

26

Enforcement &
compliance

3

0

5

1

0

0

23

Changes to the Building Code

3

1

4

0

1

0

23

Cost/benefit considerations

5

1

3

1

1

0

22

Research

5

2

1

2

1

0

22

Interface between
technologies & how they work as a system (technologies includes building
practices & techniques)

7

0

3

3

0

0

21

Pace of implementation/ incorporating feedback from stakeholders for
implementation

7

3

0

1

1

1

21

Comments and Discussion on Issues

·Philip Fairey: Real issue (1) is getting the
knowledge to the user.

·Rob Vieira:Need more research on multi-family housing.

·Roy Crawford:Need research on latent loads; Manual J for dehumidification

·Bob Cochell:Require mechanical plans.

·Steve Bassett:It all boils down to education. Have equipment. If done correctly, will
have a good indoor environment.Need to
educate consumer, sales reps.Many
directional effort re: how to design & install best system.Should be referred to the Education TAC.

·Tina Neace:As system designer, have inadequate information on how to design. Homes
are tighter & tighter.No one knows
how to do load on some new technologies.Need course on how it interfaces.

·Ivan Zuniga:AFG Glass.Have discussed proper
design considerations.Need to consider
how building code can be improved to make it simple and enforceable.

·David Martin.Viotech.Set conditions for
customer.Seems like need smarter
system; not only a thermostat, but also a humidistat.Perhaps outdoor thermostat as well.

·Philip Fairey:If going to make education the priority, would be good if it resulted in
certification.

·Dennis Stroer.Need certification of who can do calculations.

·Pete Quintela:Could code mandate design humidity & temperature?

Next Steps

·Bob Cochell.Would like to see CILB involved in education process.Need uniformity in educational process.